When performing simple tasks like pushing elevator buttons or picking up a cup, the brain actually has a mini-debate as to which hand should do the jobs. Now magnetic stimulation will make sure the brain always chooses the left hand.

Although most people are pretty clearly right- or left-handed when performing more complex tasks, like writing or handling sports equipment, almost everyone is ambidextrous when it comes to simple tasks. So in those cases, the brain's parietal cortex is charged with assessing which hand makes more sense to perform a specific task. A new study by researchers at UC Berkeley reveals this is actually a competitive process between the two hands, and it's actually possibly to disrupt the cortex's decision-making with a little transcranial magnetic stimulation, or TMS.

The researchers found that TMS disrupts the neurons in charge of motor skills, and this in turn reduced the right hand's chances of being selected to perform the simple task at hand. Instead, the left hand became the predominant choice of the test subjects, even thought most were naturally right-handed. Lead researcher Richard Ivry suspects this is just the tip of the iceberg, and TMS could also affect many other types of simple decision-making, like what sort of fruit a person wants to eat or which movie to go see.

The ability to adjust which hand a person uses also has medical applications. Ivry explains that they hope to use this research to fight learned limb disuse, in which victims of stroke and other brain injuries start favoring the arm or leg they can more easily control. This magnetic stimulation would help force the patient to use the other limbs again, helping to restore full limb movement.